In cold climates an internal combustion engine often requires the use of auxiliary heaters, such as electrical block heaters, in order to lower the viscosity of the engine lubricants and possibly to improve the vapourization of fuel, and thus provide reliable starting. Sometimes a battery warmer is also used, an in-car heater, etc., all of which are electrically operated, and typically use large amounts of power. It is the practice of many drivers to connect the electrical power to the aforenoted heaters upon parking the car in a parking lot during the day or at home in the evening. Consequently heat is generated and power is dissipated for the entire parking period, e.g., all night.
Timers, usually with a clockwork mechanism, have become available and are sometimes connected between the source of power and the automobile heater. These types of timers are usually manually set to turn the heater on after a predetermined off time. Since the heater need be turned on only a relatively short time before the automobile is to be used, it usually is on for only a fraction of the total number of hours that the automobile in unused, and significant energy savings are achieved. However it should be noted that once the timer has switched the power on, full power is applied to the heaters whether the outside temperature is near freezing, or, for instance, a very cold -20.degree. F.
The operators of parking lots in cold climates also often provide electrical outlets for supplying power to the aforenoted block heaters, etc., in order that their patrons should be able to start their autos should they return at any time during the day. Again, full power is provided whatever is the ambient temperature. In this case timers as described earlier could not satisfactorily be used by the parking lot operator since he cannot be aware of when patrons might wish to start their autos.
In order to conserve energy a home thermostat has been made available, which, under control of a timer, switches from one thermostatic setting to a second, the latter being set at a lower temperature, during sleeping hours. This thermostat therefore contains means for switching power to a furnace controlling load with changes in temperature, and means for reducing the power supplied at a given time, as set by the thermostat clock.